Problem: Simplify the following expression: $p = \dfrac{x^2 + 9x + 20}{x + 4} $
Answer: First factor the polynomial in the numerator. $ x^2 + 9x + 20 = (x + 4)(x + 5) $ So we can rewrite the expression as: $p = \dfrac{(x + 4)(x + 5)}{x + 4} $ We can divide the numerator and denominator by $(x + 4)$ on condition that $x \neq -4$ Therefore $p = x + 5; x \neq -4$